Called before the style is changed in a given range of the buffer. If the return value is #f, then the style change will be aborted. Otherwise, after-change-style is guaranteed to be called after the change has completed.
The buffer is internally locked for writing during a call to this method (see also Locks). Use after-change-style to modify the buffer, if necessary.
See also on-edit-sequence.
Dispatches to the mode.